Numerical simulation for low frequency noise from viaduct on expressway

There is the case that the low frequency noise generated complaints of neighborhood residents from the road viaduct. We tried to clarify the source of low frequency noise using the FEM model as one approach for such a problem. First, the 3D-FEM model of the vehicle, bridge, and air was constructed. Then, propagating of the acceleration was calculated by the vehicle traveling on viaduct with road irregularities. Then, the vibration velocity of the viaduct is radiated as sound pressure, and propagating of the sound pressure through the air was carried out by 3D-FEM calculation. Actually a numerical model for the viaduct that caused the complaint was constructed. The low frequency noise generation mechanism was investigated. And the effective measures was considered. As a result, it became clear that a high reduction effect of low frequency noise by performing the measures road irregularities can be obtained in the viaduct. And, it became clear that there is the acoustic radiation of low frequency noise by the sound insulation wall on the viaduct. By carrying out the parameter study using such a method, we can clarify the occurrence factor of the low frequency noise.